Oral Presentation
POLAR-2 on Chinese Space Station
Presenter: Bobing Wu (中国科学院高能物理研究所)
The Gamma-Ray Burst polarimeter POLAR, which has been launched onboard the China’s space lab “Tiangong-2” in September 2016, is a space mission dedicated for the GRB prompt emission polarization measurements in the 50-500 keV energy range, under the collaboration between Chinese and European scientists. During about 6 months of space observation, POLAR detected 55 confirmed GRBs jointly with other missions and some potential individual GRBs by itself. A polarization catalog of 14 GRBs in total has been published from POLAR in-orbit data, which is the best GRB polarization measurement results so far thanks to the high sensitivity and large field of view of the instrument, as well as the precisely calibrated systematic errors for polarization measurements. The results show that the detected GRBs are at most modestly polarized. Another new finding of the evolution of the intrapulse polarization angle provides us with a new insight into the GRB physics.
The Gamma-Ray Burst polarimetry experiment POLAR-2 mission, which is the successor of POLAR, has been accepted to be installed onboard the China Space Station experimental module dedicated to answering the questions raised by POLAR results under an enlarged China-Europe collaboration. With an improved instrument design, POLAR-2 will be able to provide a much larger sample of GRB polarization measurements with high quality and detailed polarization measurements specified as time-resolved and energy-resolved polarization analysis, thanks to the large and efficient polarimeters, and also the spectrometers which are planned to be equipped. Besides, several pulsars are expected to be seen by POLAR-2 and more stringent constraints are foreseen on the Crab pulsar polarization measurements. Currently, the POLAR-2 instruments are under development with the aim of launching around 2025.
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